Pimentel D, Williamson S, et al (2008). "Reducing energy inputs in the US food system". Human Ecology, August 2008. An estimated 19 percent of total energy used in the USA is taken up in the production and supply of food. Currently, this mostly comes from non-renewable energy sources which are in short supply. This paper, published in Human Ecology, sets out a number of strategies that could potentially cut fossil energy fuel use in the food system by as much as 50 percent.